1. Field of the Invention
The present invention relates generally to electrical safety devices, and more particularly but not exclusively to ground fault circuit interrupters.
2. Description of the Background Art
A ground fault circuit interrupter (GFCI) is an electrical device for interrupting electrical current flow upon detection of a hazardous current path to ground. GFCI's are typically employed in power outlet receptacles (e.g., 120V, 60 Hz) to prevent electrocution.
A GFCI typically includes a sense coil for sensing the difference between electrical current flowing through and returning to the GFCI. A current difference of zero indicates that all of the current is flowing to the load. A non-zero current difference indicates current leakage possibly caused by a ground fault. The sense coil senses this leakage current and provides corresponding information to a GFCI controller, such as the RV4141A integrated circuit (IC) device from Fairchild Semiconductor. In response to a ground fault, the GFCI controller generates a fault signal to turn ON a silicon controlled rectifier (SCR), which in turn energizes a solenoid to open load contacts and cut-off power to the load.
The Consumer Product Safety Commission recommends that GFCI's be tested on a monthly basis. GFCI manufacturers are thus required to include test and reset buttons for manually verifying proper operation of a GFCI device. Unfortunately, most GFCI's are not manually tested for functionality. Accordingly, there is a need for some form of GFCI self test.
One way of self testing a GFCI is to automatically trip the GFCI and then reset it. This approach is undesirable because it would cause temporary power loss, unexpectedly interrupting operation of electronic devices plugged into the power outlet receptacle (e.g., could cause data loss). Embodiments of the present invention pertain to a GFCI that allows for self testing of critical components without load power loss.